The two trains, each with four cars, collided head-on in an olive grove on flat terrain between the towns of Andria and Corato on a line with just a single track

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This aerial handout photo shows what is left of two commuters trains after their head-on collision in the southern region of Puglia, Tuesday, July 12, 2016. At least 20 people were killed.

Two Italian commuter trains collided head-on Tuesday in the southern region of Puglia, killing at least 22 people and injuring scores more, officials said. At least two passengers were pulled alive from the crumpled wreckage as the rescue operation ground on in the scorching heat.

Railway police Commander Giancarlo Conticchio told Sky TG24 said that the number of dead was 22 with 43 people injured, adding that the final toll could still be higher.

The two trains, each with four cars, collided head-on in an olive grove on flat terrain between the towns of Andria and Corato on a line with just a single track. The accident occurred around 11:30 a.m. some 50 kilometers (30 miles) northwest of the Puglia regional capital, Bari.

"It's a disaster as if an airplane fell," Corato Mayor Massimo Mazzilli said on his Facebook page, where he posted photos of the crash.

Italian Premier Matteo Renzi pledged a thorough investigation and returned to Rome from Milan to monitor the situation. His transport minister, Graziano Delrio, as well as local prosecutors were at the scene.

"We must begin to understand the causes of this tragedy that has saddened the whole country," Delrio said at the site, announcing a commission of inquiry. "The crash was certainly violent. Extremely violent."

The trains were operated by a private, Bari-based rail company, Ferrotramviaria, that connects the city of Bari with Puglia towns to the north and the airport. Ferrotramviaria's website said its fleet comprises 21 electric trains, most with four cars each. The line serves mostly students and commuters.

In a phone interview with state TV, Ferrotramviaria director general Massimo Nitti said the dynamics of what went wrong are still to be determined, but it is clear "one of the trains wasn't supposed to be there" at the same time as the other.